The present invention relates to grommets for the installation of wiring harnesses through a truck firewall. More specifically, the present invention relates to a variable diameter grommet which is capable of accepting wire harnesses which range in diameter from 1/2 to 11/4 inch.
The use of grommets as a second conduit for passing wiring harnesses through a truck firewall is generally well known in the art. A grommet is basically a rubber device (although other materials can be used) through which a plurality of wires, referred to as a "wiring harness," are passed. A sealer such as putty is utilized in prior art embodiments to form a complete seal between the wiring harness and the grommet. The placement of a grommet in a firewall is generally illustrated in FIG. 3.
The function of a grommet is to pass the main electronic wires from the engine to the interior of a truck cab. As modern technology advances, more and more aspects of a truck engine are becoming electronic and, therefore, require signal lines passing through a truck firewall to the truck cab where operating conditions are displayed on the dash panel. Another factor affecting the volume of wires passing between the engine and cab of a truck is the fact that a substantial number of truck cabs are custom built and, therefore, although the chassis are constructed on the same assembly line, a different wiring configuration will be needed for different trucks. This presents a problem with the use of prior art grommets which have only a fixed opening and, therefore, necessitate the use of extraneous materials to produce a tight fit between a wiring harness and a grommet.
In addition to having a fixed opening, prior art grommets suffer from several other shortcomings. These grommets resemble a donut in that they are configured of a solid piece of material with a hole therethrough. This requires all electrical wires between the engine and the cab to be grouped in one location and fed through the grommet into the truck cab after which the grommet is inserted in the firewall. The grouping of all electrical wires to a singular location before entering into the grommet is a cumbersome task on an assembly line. Ease and economy would be furthered by connecting a wire through the firewall during initial installation of a part from which a wire extends.
Since the prior art grommets have a fixed opening therethrough, putty is used to plug the extra space created between a wiring harness and a grommet. The putty also suffers from several shortcomings. For example, putty deteriorates and falls out completely with time. Additionally, the putty is unsightly and difficult to work with, necessitating a considerably longer time to install. Moreover, there is no objective control of putty installation on an assembly line. It is not only easily forgotten, but creates a quality control problem in that one assembly line worker may put on a little putty and the next a lot of putty.